1. Technical Field of the Invention
This invention relates to a method for the production of N-methylmorpholine oxide. More particularly, this invention relates to a method wherein N-methylmorpholine is reacted with aqueous hydrogen peroxide in an atmosphere consisting essentially of carbon dioxide in order to provide a reaction product consisting essentially of N-methylmorpholine oxide, the reaction product being contaminated with less than 25 parts per billion of nitrosamine impurities.
2. Prior Art
Bauer et al. European patent application 0,307,184, filed Jul. 9, 1988, discloses a method for the preparation of tertiary amine oxides substantially free from nitrosamine byproducts wherein a tertiary amine is reacted with aqueous hydrogen peroxide in the presence of carbon dioxide at a temperature of 45.degree. C. or less. The preferred amine starting materials are alkyl amines. N-methyl morpholine is mentioned, but there is no mention of the discovery herein that N-methyl morpholine is a unique feedstock in that N-methyl morpholine oxide substantially free from nitrosamine by-products can be prepared by reacting N-methyl morpholine with hydrogen peroxide in the presence of carbon dioxide at reaction temperatures of 50.degree. to 100.degree. C.
Murata et al. U.S. Pat. No. 4,247,480 is directed to a method for the preparation of amine oxides wherein a tertiary amine is oxidized in the presence of carbon dioxide and a promoter such as ethylenediaminetetraacetic acid, stanates, polyphosphates, etc. The oxidant that is used is hydrogen peroxide.
Bauer et al. U.S. Pat. No. 4,994,614 is also directed to a process for the preparation of tertiary amine oxides by the reaction of a tertiary amine with hydrogen peroxide in the presence of carbon dioxide and ascorbic acid. The stated advantage of the process is the provision of tertiary amine oxides that are substantially free from nitrosamine byproducts. It is stated that the results were unexpected because under the same reaction conditions amine oxides made in the presence of either carbon dioxide or ascorbic acid individually contain significant quantities of nitrosamines. A wide variety of tertiary amines are mentioned as feedstocks including dialkyl amines, triaryl amines, mixed alkyl aryl, alkyl-arylalkyl, aryl-arylalkyl or alkyl-aryl-arylalkylamines including also heterocyclic amines such as N-methyl piperidine, N,N'-dimethyl piperazine, pyridine, 2-methyl pyridine, N-methyl pyrrolidine, N-methyl pyrrolidone, N-methyl morpholine, N-ethyl morpholine, and the like.
European Patent Application No. 0,356,918 discloses a process for preparing amine oxides having decreased levels of nitrosamine contamination by reacting a tertiary amine with hydrogen peroxide in the presence of titanium alone or in the combined presence of titanium and carbon dioxide.
European Patent No. 0,409,043 discloses a process for the preparation of amine oxides having reduced nitrosamine contamination by the reaction of a tertiary amine with hydrogen peroxide in the presence of alkyleneaminopoly(methylenephosphonic acid).